Compositions of pentafluoropropane and dichlorotrifluoroethane

ABSTRACT

Compositions of 1,1,1,3,3 -pentafluoropropane and 1,1 -dichloro-2,2,2-trifluoroethane are provided. The compositions of the invention are environmentally desirable for use as refrigerants, aerosol propellants, blowing agents for polymer foam, heat transfer media, gaseous dielectrics and solvents.

This appln claims benefit of Prov. No. 60/113,687 filed Dec. 24, 1998.

FIELD OF THE INVENTION

The present invention relates to mixtures of1,1,1,3,3-pentafluoropropane (“HFC-245fa”) and1,1-dichloro-2,2,2-trifluoroethane (“HCFC-123”). More particularly, theinvention provides compositions of HFC-245fa and HCFC-123 that areenvironmentally desirable for use as refrigerants, in centrifugalchillers, aerosol propellants, metered dose inhalers, fireextinguishers, blowing agents for polymer foam, heat transfer media,gaseous dielectrics, and solvents.

BACKGROUND OF THE INVENTION

Fluorocarbon based fluids have found widespread use in industry in anumber of applications, including as refrigerants, aerosol propellants,blowing agents, heat transfer media, and gaseous dielectrics. Because ofthe suspected environmental problems associated with the use of some ofthese fluids, it is desirable to use fluids of lesser ozone depletionpotential such as hydrofluorocarbons, (“HFC's”) and/orhydrochlorofluorocarbons (“HCFC's”).

Thus, the use of fluids that do not contain CFC's or contain HCFC'sinstead of CFC's is desirable. Additionally, it is known that the use ofsingle component fluids or azeotropic mixtures, which mixtures do notfractionate on boiling and evaporation, is desirable. However, theidentification of new, environmentally safe, azeotropic mixtures iscomplicated due to the fact that it is difficult to predict azeotropeformation.

The art continually is seeking new fluorocarbon based mixtures thatoffer alternatives, and are considered environmentally safe substitutes,for CFC's and HCFC's. Of particular interest are mixtures containing afluorocarbon and hydrochlorocarbon both of low ozone depletionpotentials; it is these mixtures that are the subject of this invention.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

This invention provides azeotrope-like and nonazeotrope-likecompositions of HFC-245fa and HCFC-123. The compositions of theinvention provide environmentally desirable for currently used CFC's andHCFC's since HFC-245fa and HCFC-123 have zero and very low ozonedepletion potentials, respectively. Additionally, the compositions ofthe invention exhibit characteristics that make the compositions betterCFC and HCFC substitutes than either HFC-245fa or HCFC-123 alone.

One embodiment of the invention provides azeotrope-like compositionscomprising effective amounts of HFC-245fa and HCFC-123. By “effectiveamounts” is meant the amount of each component that, on combination withthe other component, results in the formation of an azeotrope-likecomposition. More specifically, the invention provides azeotrope-likecompositions preferably of from about 90 to about 99 weight percentHFC-245fa and from about 10 to about 1 weight percent HCFC-123 having aboiling point of 15° C.±2, preferably±1° C., at 760 mm. The preferred,more preferred, and most preferred compositions of the invention are setforth in Table 1. The numerical ranges in Table 1 are to be understoodto be prefaced by the term “about”.

TABLE 1 More Most Components Preferred (wt %) Preferred (wt %) Preferred(wt %) HFC-245fa 90-99 94-99 97-99 HCFC-123 10-1   6-1   3-1 

For purposes of this invention, azeotrope-like compositions arecompositions that behave like azeotropic mixtures. From fundamentalprinciples, the thermodynamic state of a fluid is defined by pressure,temperature, liquid composition, and vapor composition. An azeotropicmixture is a system of two or more components in which the liquidcomposition and vapor composition are equal at the state pressure andtemperature. In practice, this means that the components of anazeotropic mixture are constant boiling and cannot be separated during aphase change.

Azeotrope-like compositions behave like azeotropic mixtures, i.e., areconstant boiling or essentially constant boiling. In other words, forazeotrope-like compositions, the composition of the vapor formed duringboiling or evaporation is identical, or substantially identical, to theoriginal liquid composition. Thus, with boiling or evaporation, theliquid composition changes, if at all, only to a minimal or negligibleextent. This is to be contrasted with non-azeotrope-like compositions inwhich, during boiling or evaporation, the liquid composition changes toa substantial degree. All azeotrope-like compositions of the inventionwithin the indicated ranges as well as certain compositions outsidethese ranges are azeotrope-like.

The azeotrope-like compositions of the invention may include additionalcomponents that do not form new azeotropic or azeotrope-like systems, oradditional components that are not in the first distillation cut. Thefirst distillation cut is the first cut taken after the distillationcolumn displays steady state operation under total reflux conditions.One way to determine whether the addition of a component forms a newazeotropic or azeotrope-like system so as to be outside of thisinvention is to distill a sample of the composition with the componentunder conditions that would be expected to separate a nonazeotropicmixture into its separate components. If the mixture containing theadditional component is nonazeotropic or nonazeotrope-like, theadditional component will fractionate from the azeotropic orazeotrope-like components. If the mixture is azeotrope-like, some finiteamount of a first distillation cut will be obtained that contains all ofthe mixture components that is constant boiling or behaves as a singlesubstance.

It follows from this that another characteristic of azeotrope-likecompositions is that there is a range of compositions containing thesame components in varying proportions that are azeotrope-like, orconstant boiling. All such compositions are intended to be covered bythe terms “azeotrope-like” and “constant boiling”. As an example, it iswell known that at differing pressures, the composition of a givenazeotrope will vary at least slightly as does the boiling point of thecomposition. Thus, an azeotrope of A and B represents a unique type ofrelationship, but with a variable composition depending on temperatureand/or pressure. It follows that, for azeotrope-like compositions, thereis a range of compositions containing the same components in varyingproportions that are azeotrope-like. All such compositions are intendedto be covered by the term azeotrope-like as used herein.

In another embodiment of the invention, nonazeotrope-like compositionsare provided which compositions comprise HFC-245fa and HCFC-123 andwhich have a vapor pressure of about 18 psia to about 19 psia at 20° C.Preferably, the compositions of the invention comprise from about 90 toabout 99 weight percent HFC-245fa and from about 10 to about 1 weightpercent HCFC-123a. The preferred, more preferred, and most preferredcompositions of this embodiment are set forth in Table 2. The numericalranges in Table 2 are to be understood to be prefaced by the term“about.”

TABLE 2 More Most Components Preferred (wt %) Preferred (wt %) Preferred(wt %) HFC-245fa 90-99 94-99 97-99 HCFC-123 10-1   6-1   3-1 

The compositions of the invention meet the need in the art for CFC/HCFCmixtures that have a low ozone depletion potential and are negligiblecontributors to greenhouse global warming, are nonflammable, and have anappropriate compressor discharge temperature. Additionally, thecompositions of the invention offer superior refrigeration capacity whencompared to such fluids as HFC-245fa or HCFC-123 alone. Further, becausethe azeotrope-like compositions of the invention exhibit constant vaporpressure characteristics and relatively minor composition shifts as theliquid mixture is evaporated, the azeotrope-like composition of theinvention are comparable to a constant boiling single componentrefrigerant or an azeotropic mixture refrigerant.

In a process embodiment, the compositions of the invention may be usedin a method for producing refrigeration that comprises condensing arefrigerant comprising the azeotrope-like or nonazeotrope-likecompositions of this invention and thereafter evaporating therefrigerant in the vicinity of a body to be cooled. In yet anotherprocess embodiment, the compositions of the invention may be used in amethod for heating that comprises condensing a refrigerant comprisingthe azeotrope-like or nonazeotrope-like compositions of the invention inthe vicinity of a body to be heated and thereafter evaporating therefrigerant.

In another embodiment, the compositions of the invention may be used incentrifugal chillers. By “centrifugal chillers” is meant refrigerationequipment that uses centrifugal compression to compress the refrigerant.The invention provides a method for producing refrigeration using acentrifugal compressor comprising compressing a refrigerant comprisingthe azeotrope-like or nonazeotrope-like compositions of the inventionand thereafter evaporating the refrigerant in the vicinity of a body tobe cooled.

In still another embodiment, the compositions of the invention may beused in a method for producing foam comprising blending a heatplasticized resin with a volatile bowing agent comprising theazeotrope-like or nonazeotrope-like compositions of the invention andintroducing the resin/volatile blowing agent blend into a zone of lowerpressure to cause foaming.

In another process embodiment, the compositions of the invention areused in method for producing polyurethane and polyisocyanurate foams.Any of the methods well known in the art such as those described in“Polyurethanes Chemistry and Technology,” Volumes I and II, Saunders andFrisch, 1962, John Wiley and Sons, New York, N.Y.. In general, themethod comprises preparing polyurethane or polyisocyanurate foams bycombining an isocyanate, a polyol or mixture of polyols, a blowing agentor mixture of blowing agents, and other materials such as catalysts,surfactants, and optionally, flame retardants, colorants, or otheradditives. The blowing agent or agents employed shall be a volatilemixture of the azeotrope-like or nonazeotrope-like compositions of thepresent invention.

It is convenient in many applications to provide the components forpolyurethane or polyisocyanurate foams in preblended formulations. Mosttypically, the foam formulation is preblended into two components. Theisocyanate and optionally certain surfactants and blowing agentscomprise the first component, commonly referred to as the “A” component.The polyol or polyol mixture, surfactant, catalysts, blowing agents,flame retardant, and other isocyanate reactive components comprise thesecond component, commonly referred to as the “B” component.Accordingly, polyurethane and polyisocyanurate foams are readilyprepared by bringing together the A and B side components either by handmix for small preparations and, preferably, machine mix techniques toform blocks, slabs, laminates, pour-in-place panels and other items,spray applied foams, froths, and the like. Optionally, other ingredientssuch as fire retardants, colorants, auxiliary blowing agents, water, andeven other polyols can be added as a third stream to the mix head orreaction site. Most conveniently, however, they are all incorporatedinto one B component as described above.

It is also possible to produce thermoplastic foams using thecompositions of the invention. For example, conventional foampolyurethanes and isocyanurate formulations may be combined with theazeotrope-like or nonazeotrope-like composition in a conventional mannerto produce rigid foams.

Azeotrope-like and nonazeotrope-like mixtures containing HFC-245fa areparticularly suitable as foam blowing agents since foams blown withHFC-245fa have been found to possess low relative initial and agedthermal conductivity and good dimensional stability at low temperatures.Of particular interest are those mixtures that contain HFC-245fa andother zero or low ozone depletion HFC's and/or HCFC's.

The compositions of the invention may also be used as heat transferfluids. For example, in certain refrigeration systems, it is desirableto operate the system at a specific temperature. However, maintainingthe desired temperature may require either the addition or removal ofheat. Thus, a secondary heating loop containing an appropriate heattransfer fluid may be added. The heat transfer fluid absorbs heat in onepart of the cycle and transfers the heat to another part of the cyclewithout changing state, when the heat transferred is sensible, or bychanging state, when the heat transferred is latent.

In another embodiment, the mixtures and compositions of this inventionmay be used as propellants in sprayable compositions, either alone or incombination with known propellants. The sprayable composition comprises,consists essentially of, and consists of a material to be sprayed and apropellant comprising, consisting essentially of, and consisting of amixture or composition of the invention. Inert ingredients, solvents,and other materials may also be present in the sprayable mixture.Preferably, the sprayable composition is an aerosol. Suitable materialsto be sprayed include, without limitation, cosmetic materials such asdeodorants, perfumes, hair sprays, cleansers, and polishing agents aswell as medicinal materials such as anti-asthma and anti-halitosismedications.

The compositions of the invention may also be used in a method ofdissolving contaminants or removing contaminants from the surface of asubstrate, which method comprises the step of contacting the substratewith the compositions of the present invention. In another embodiment,the compounds and mixtures of the present invention may also be used asfire extinguishing agents.

The components of the composition of the invention are known materialsthat are commercially available or may be prepared by known methods.Preferably, the components are of sufficiently high purity so as toavoid the introduction of adverse influences on the properties of thesystem.

Additional components may be added to tailor the properties of thecompositions of the invention as needed. By way of example, oilsolubility aids may be added in the case in which the compositions ofthe invention are used as refrigerants.

The present invention is more fully illustrated by the followingnon-limiting examples.

EXAMPLES Example 1

An ebulliometer consisting of a vacuum-jacketed tube with a condenser ontop was used. About 11.3 g HFC-245fa were charged to the ebulliometerand HCFC-123 was added in small, measured increments. The temperaturewas measured using a platinum resistance thermometer. From about 0 toabout 0.8 weight percent HCFC-123, the boiling point of the compositiondid not change. Therefore, the composition boils as a constant-boilingcomposition over this range.

Example 2

An ebulliometer consisting of a vacuum-jacketed tube with a condenser ontop was used. About 16.7 g HFC-245fa were charged to the ebulliometerand HCFC-123 was added in small, measured increments. The temperaturewas measured using a platinum resistance thermometer. From about 0 toabout 1.7 weight percent HCFC-123, the boiling point of the compositionchanged by only 0.02° C. Therefore, the composition boils as aconstant-boiling composition over this range.

Example 3

This example demonstrates that constant-boiling blends of HFC-245fa andHCFC-123 have certain advantages compared to either HFC-245fa orHCFC-123 alone. The theoretical performance of a refrigerant at specificoperating conditions can be estimated from the thermodynamic propertiesof the refrigerant using standard refrigeration cycle analysistechniques. See, e.g., R. C. Downing Fluorocarbon Refrigerants Handbook,Prentice Hall (1988). The coefficient of performance, COP, is auniversally accepted measure especially useful in representing therelative thermodynamic efficiency of a refrigerant in a specific heatingor cooling cycle involving evaporation or condensation of a refrigerant.This term expresses the ratio of useful refrigeration to the energyapplied by the compressor in compressing the vapor. The capacity of arefrigerant represents the volumetric efficiency of the refrigerant.This value expresses the capability of a compressor to pump quantitiesof heat for a given volumetric flow rate of refrigerant. In other words,given a specific compressor, a refrigerant with a higher capacity willdeliver more cooling or heating power.

This type of calculation is performed for an air conditioning cycle inwhich the condenser temperature was 110° F. and the evaporatortemperature was 35° F. Compression efficiency of 85 %, superheat of 20°F., and a subcooling of 10° F. were assumed. Calculations were performedfor various combinations of HFC-245fa and HCFC-123 and for HFC-245fa andHCFC-123 as single components. Table 3 lists the COP and capacities ofthe compositions of the invention relative to HFC-245fa and HCFC-123.

TABLE 3 Thermodynamic Performance Refrigerant COP Capacity (cfm)HCFC-123 4.85 540 HFC-245fa/HCFC-123 4.76 833 (99/1 wt %)HFC-245fa/HCFC-123 4.76 833 (97/3 wt %) HFC-245fa/HCFC-123 4.77 831(94/6 wt %) HFC-245fa/HCFC-123 4.77 829 (90/10 wt %) HFC-245fa 4.70 812

As Table 3 illustrates, the compositions of the invention are betterthan either pure component HFC-245fa or HCFC-123 in terms ofrefrigeration capacity, and are comparable in terms of COP.

Example 4

40 g of each of the azeotrope-like compositions given in Table 1 arecharged into individual 200 cc sealed vessels containing 3 g on Dowstyrene 685D. The vessels are placed in a 250° F. oven overnight.Twenty-four hours later, the vessels are removed from the oven andrapidly depressurized. The resulting foams are inspected and found to beof good quality.

Example 5

This example illustrates the use of preferred azeotrope-likecompositions of the invention to clean (deflux) printed wiring boardsand printed wiring assemblies. A commercial rosin based flux viz. Kenco885 (manufactured by Kenco Industries, Inc.) is used in this test.

In the experiment FR-4 eoxy coupons cut to a size of 1″×2.25″ are usedfor flux and subsequent cleaning. Prior to fluxing all specimen areprecleaned to ensure very low levels of contamination before fluxing.The contamination is measured by measuring conductivity of the washsolution (in equivalent micrograms of sodium chloride) per square inchof the boards using a conductivity bridge. (See U.S. Pat. No.4,816,175). Using this technique, it is determined that all specimensare precleaned to 0.05 micrograms or less of sodium chlorideequivalents.

A measured amount of Kenco 885 flux is applied to each of the coupons.The coupons are air dried and dried at 90 C for 5 minutes and baked at230 C for 1 minute. This procedure mimics the Hollis wave soldermachine. The amount of ionic materials left in the board after thedrying process is of the same order of magnitude as in a wave soldermachine.

These fluxed coupons are then cleaned in the boiling solvents for twominutes, after which the amount of ionics is washed off by a 75/25 byweight water/isopropanol (IPA) mixture for 24 hours. The conductivity ofthe water/IPA mixture is measured as described previously.

The cleaning study results show that the solvent (245fa/123) mixtures ofthe invention remove ionic impurities much more efficiently than 245faalone.

What is claimed is:
 1. Azeotrope-like compositions consisting essentially of an effective amount of 1,1,1,3,3-pentafluoropropane and 1,1 -dichloro-2,2,2-trifluoroethane which compositions boil at about 15° C.±2° C. at 760 mm Hg.
 2. The compositions of claim 1 consisting essentially of from about 99 to about 90 weight percent 1,1,1,3,3-pentafluoropropane and from about 1 to about 10 weight percent 1,1 -dichloro-2,2,2-trifluoroethane.
 3. The compositions of claim 1 consisting essentially of from about 99 to about 94 weight percent 1,1,1,3,3-pentafluoropropane and from about 1 to about 6 weight percent 1,1 -dichloro-2,2,2-trifluoroethane.
 4. The compositions of claim 1 consisting essentially of from about 99 to about 97 weight percent 1,1,1,3,3-pentafluoropropane and from about 1 to about 3 weight percent 1,1-dichloro-2,2,2-trifluoroethane.
 5. Compositions comprising 1,1,1,3,3-pentafluoropropane and 1,1-dichloro-2,2,2-trifluoroethane having a vapor pressure of from about 18 psia to about 19 psia at 20° C.
 6. The compositions of claim 5 consisting essentially of 1,1,1,3,3-pentafluoropropane and 1,1-dichloro-2,2,2-trifluoroethane. 